Liang Guoling, Zhang Yongbo, Zhang Lizhong, Zhou Xiaoyuan, Zhang Chunying

(Institute of Hydrogeology and Environmental Geology, CAGS, Shijiazhuang, 050061)

[1][1] Part of study results for the Project "New Round All-China Groundwater Resource Assessment"(K5.4, Project code 0299209078), Land and Resources Investigation Project.

E-mail: Lguoling_iheg@163.com

Abstract: The database of groundwater resource in China is the part of research achievements of "New Round Nationwide Groundwater Resource Assessment"sponsored by the Ministry of Land and Resources. It contains the spatial and attribute information of groundwater resource and environment and it has realized digitalization information flow from the paper media for representing the achievements and has laid a foundation for realizing the data sharing on larger extent. The paper deals with designing thought and construction process of groundwater resource database in respect of its overall structure, standardization of groundwater resource information, map layer division, data gathering, technical flowing process and quality control system.

Key words: database, map layer, data gathering

The groundwater resource is the important factor for ensuring the water supply for the people and supporting the social economic development. To further investigate and assess the groundwater resource status in China is important basis for rational exploitation and utilization of water resources and for making up the planning for the regional economy and state policy as well. The new round all-China groundwater resource assessment is the project of land resource investigation, which reassesses the nationwide groundwater resource and environmental problems related to groundwater resource development. The all-China groundwater resource database system is the digitalization achievements of the said project, which systematically stores and administrates all the data concerning all-China, each region, each province (municipality, autonomous region) and more accurately reflects and spreads the groundwater map of China and spatial information and relation with the attribute information. The achievements accord with the needs for data by the modern society and realize the change from the paper medium to digitalized information, laying the foundation for realizing the data sharing on larger extent.

1       Structure Designing of Groundwater Resource Database

In order to correctly describe the outline of all-China groundwater resource data and reflect the features of groundwater resource data, overall and systematical analysis to the data structure of groundwater resource should be made and standard data model of groundwater resource should be set up before gathering all-China groundwater resource data and designing the spatial database.

1.1 Data analysis

All-China groundwater resource database is map-based spatial database, which not only covers spatial vector data, but also is in possession of graph attribute feature, these enrich the content of the map. The data mainly contains groundwater resource investigation and comprehensive assessment information, of which the content can be divided into: groundwater resource zonation, groundwater resource distribution, groundwater resource exploitation and utilization, groundwater chemistry, groundwater environment. The groundwater resource zonation is managed by the administrative division and groundwater system zonation; The groundwater resource distribution mainly describes the groundwater resource spatial distribution status and distribution characteristics; The groundwater exploitation and utilization reflect groundwater resource exploitation, exploitation potential and groundwater water supply status in main cities; The groundwater chemistry and groundwater environment describe groundwater chemical features, groundwater quality assessment, aquifer vulnerability analysis and the various environmental problems caused by the groundwater exploitation.

1.2 Data structure designing

Based on the analyzing the data and information concerning all-China groundwater resource investigation and assessment and in combination with the clients' demand, the data and information will be divided into five categories and each categories will further divided as Fig.1, thus, the structure model and interrelation of the groundwater resource data and information will be established.

2         Groundwater Resource Database Standard

The all-China groundwater resource database involves many types of data and is comparatively complicated. In order to realize the orderly and standardization management and ensure the smooth establishment of the database, when the unified standard for establishing the database is made out, the existing state standards or professional standards should be closed with. Generally the spatial database construction standard formulated by the China Geological Survey should be cited.

2.1 Spatial database map layer denomination and division standard

The spatial database is the data integration that the spatial data and information will be represented in the digitalized form. The map layer is the integration of same feature of geographic substance in the certain spatial extent. The map layer in the groundwater resource database of China represents all content of groundwater resource spatial database. In order to realizing convenient use and scientific management of the database map layer, it is needed to make out the rational and effective map layer denomination principles, which can correctly and clearly recognize each database map layer. The database map layer will be denominated based on the following coding patterns:

Fig. 1 Groundwater resource data structure of China (1)

Fig. 1 Groundwater resources data structure of China (2)

Fig. 1 Groundwater resource data structure of China (3)

Fig. 1 Groundwater resources data structure of China (4)

Fig. 1 Groundwater resource data structure of China (5)

The map layer denomination can be divided into three categories: type code, professional recognition code and map layer order code. The map layer name is composed of seven codes. The first two are type code, then the following three are professional recognition code and the last two are map layer order code (Table 1).

Table 1 Comparison of type code and profession code

To correctly and rationally divide the map layer is the key step for the database construction, and professional content classification of data is the important basis of the data lamination, so not only the feature and characteristics of the data should be taken into consideration, but also the overall structure of the database should be taken into consideration. All the data with regards to the professional characteristics should be classified in unity and the map layer division plan should be determined based on the established structure model and relation of groundwater resource data (Table 2).

Table 2 Map layer division, denomination and corresponding attribute table of database

of the groundwater resource in China

Table 2 (continued) Map layer division, denomination and corresponding attribute

table of database of the Groundwater resources in China

Notes: ## is the type code.

2.2 Map unit coding system

The map unit is the basic unit of the map layer, and the map unit coding is the only sign of the map unit and the key word linking the map unit and the attribute. The map unit coding should also follow a certain coding rules to link correctly with the attribute, showing its real meaning. The map unit is composed of eight digits, the first two is the type code to represent whole country, big regions or provinces, the following three digits are map layer recognition codes, composed of spelling letter representing the map layer, the last three digits are order code, order coding by the natural range.

2.3 Spatial database attribute table designing

The attribute is the reflection of the spatial substance, the map unit attribute table further describes the internal features (including quality feature, quantity feature and relation feature) of the map unit and is represented in the two-dimensional form. In the attribute table designing, feature of the spatial data should be taken into full consideration and the attributes of all kinds should be correctly analyzed and defined so that the attribute structure accurately reflects data feature of substance and avoids data verbosity so as to meet the requirements of clients and make the attribute table structure rationalization and standardization. With this end in view, the corresponding attribute tables of all map layers in the all-China groundwater resource database and its standard structure have been compiled according to the professional features based the comprehensive analysis to the data. The map unit attribute can be divided into two types: internal attribute, namely, map unit and attribute is the one-to-one relation and outer attachment attribute, namely, one map layer at same time is corresponding to a few attributes and is related to the attribute with map unit code, realizing that one map unit can be corresponding to a few attributes.

3       Technical Procedure of Groundwater Resource Database Construction

To make out the spatial database construction technical procedure is the important step for restraining the input and edition process of the database to ensure the database construction quality. The technical procedure runs through the whole process of the database construction, which can be divided into five stages: Database construction preparation and data preprocessinggraphic data gathering and processingattribute data gathering and processingdigital mappingdata integration (Fig. 2).

3.1 Graphic data gathering and processing

The important factor affecting the gathering quality and precision of the graphic data is the set-down of the gathering data standard, thus, in the data gathering process, the database construction standard must be implemented strictly as follows:

(1)The scanning vector should be taken during the graphic data gathering with the precision of color scanning over 150DPI and black and white scanning over 300DPI.

(2)The graphic vector will be carried out in the alternation form, the point element has been gathered from its geometrical center and the linear element is gathered by way of central line tracking bedding vector. The element gathering of the map is completely inosculating with the scanning data.

(3)The digitalized projection pattern of the graph is consistency with that of the corresponding base map.

(4)The graphic data gathering should be taken by layer, the graphic element can not be missed or input in repetition. When one map layer needs the content of another map layer, the copy should be made instead of input again. So the digitalized input of the map layer must follow strict order.

(5)in the process of graphic vector, the error correction must be made because there is the error between the graph and theoretical value.

(6)To make the topology processing layer by layer according to the division of the map layer in the construction of the database and to avoid the occurrence of incorrect suspending joint, false joints and suspending arch section so as to the revision of the topology relation between map layers. A correct topology relation is the basis and precondition for graphic operation and calculation.

(7)To ensure the correctness of professional map layer and geographic base map layer.

3.2 Attribute data gathering and processing

The attribute data can be classified into two types, one is graphic based internal attribute, which co-existing with the graphic data and are stored in the MAPGIS format; another are external attribute, which can be existing independently and are stored in the ACCESS format and realizes the linking of map layer and attribute. The following principles should be observed in the attribute data gathering:

To strictly follow the database attribute structure standard to input the internal attribute and outer attachment attribute data of the map unit of each map layer.

To make the examination to the all input attribute data to guarantee the correctness of the data to the database and the consistency of the graphic data and attribute data.

To fill in the data file to explain the source and reliability of the data when finishing each graphic data and attribute data gathering.

3.3 Digital mapping

The digital mapping is a main content of present database construction, and is also one of the representation of the research results. The digital mapping should also follow the standardization, thus, the digital mapping in the construction of the China groundwater resource database strictly follows the mapping standard stipulated in the project “New round nationwide groundwater resource assessment”. In addition to the gathering of above said graphic data, the digital mapping also includes the setup of the map frame, non-professional content input of map layer, the editing of the point and line parameters, the color designing of the polygon and notation. Then the s series of achievement maps will be formed. All the work of digital mapping is done with the MAPGIS software.

3.4 Database integration

(1)Spatial data and non-spatial data integration

Based on the spatial database (graphical database) and non-spatial database (pure attribute database), to link the two databases through the key word of map unit code and make the consistency examination of map unit and attribute, thus, finishing the construction of the database.

(2) Projection transformation and data format

Because the data are involved with extensive area (all-China, seven big regions and thirty-two provinces, autonomous regions and municipalities) and the map scales are different, so the projection parameters are different. With the regards to the actual conditions, all achievements data are projected according to the geographic base map of the actual map. The graphic data are the MAPGIS format and the attribute data are the format.

(3) Database and management application software integration

To construct a database management application system at the same time with the database construction, and to finish the integration of the database and database management application software so as to form the complete the China groundwater resource database system which will be burned to the disc for realizing the systematic and scientific management to the groundwater resource data and providing the service for the data browse, inquiry and output of the inquiry results.

4 Spatial Database Quality Control

The accuracy and reliability of a better spatial database system is very important, so it is required that the perfect data quality controlling system should be established in the process of the database construction to ensure the correctness of the data. The measures should be taken as follows:

(1)  To establish the perfect working log, the operator must write the working log according to the requirements, including working process, working method and problems encountered. The records should be underwritten by the superattendant.

(2)  To establish the complete self-examination table, each operator should carefully examine the map after finishing the work and write down the self-examination and correction results which are finally signed by the superattendant. Based on the self-examination, the project leader arranges other people to examine again with the examination ratio no less than 60%, and then write down the self-examination and correction records, which are finally signed by the superattendant.

(3)  To make stage data examination, namely, to make the strict examination to the important achievements of each database construction stage, such as map element examination of map scanning vector, the examination of map unit and element after the attribute input, veracity examination of map layer matching, and the topology consistency examination.

(4)  To organize the specially-assigned person to make the sample examination with the ratio no less than 10%, these not up to the quality requirements should be done again or amended so as to ensure the examination content completely according with the quality requirements.

(5)  To make the quality check to the map, namely, the check to the output all essential color maps, to make the proper treatment in time on finding the pretermission or repetition for the guarantee of the data correctness.

5 Conlcusion

With the rapid development and application of information technique nowadays, the digitalization achievements with the database as the representative have become the part of comprehensive achievements in the national land and resources investigation. The data is the basis of the study and the scientific and systematical management of data for the better service to the society is the important task in the future.